This invention relates to a printer, and more particularly to a printer wherein impact printing and non-impact printing can be selectively effected as required by a combination of a developing unit for forming a toner image with a print head of the common impact type.
Generally, printers are divided roughly into those of the impact type as represented by a wire dot printer and those of the non-impact type as represented by an electrophotographic printer. Printers of the impact type have a characteristic that they are suitable for printing with a plurality of copies while printers of the non-impact type have a characteristic that they have a high resolution and allow printing at a relatively high speed.
Meanwhile, some of printers of the impact type of a high grade in recent years are provided with a paper transport device which automatically supplies one after another of paper sheets stored in a pile in a supply paper tray to a position between a print head and a platen and discharges a paper tray after printing onto a discharge paper tray.
However, since conventional printers are either of the impact type or the non-impact type as described above, it is impossible for both of them to selectively make the most of the characteristics of both types.